1. Field of the Disclosure
The present invention relates to device and method for forming a thin film pattern which can maintain an extent of wetting of a printing liquid at a proper state without time dependence.
2. Discussion of the Related Art
Recently, various kinds of flat display devices have been developed, which can reduce weight and volume that are disadvantages of a cathode ray tube. In the flat display devices, there is a liquid crystal display device, a field emission display device, a plasma display panel, an electroluminescence EL display device, and so on.
The flat display device is provided with a plurality of thin films formed by a mask process including a deposition step, an exposure step, a development step, an etching step, and so on. However, since the mask process has a complicate fabrication process, the mask process increases a production cost. Consequently, researches for forming the thin film by using a printing process utilizing a printing roller are under progress.
The printing process is a process in which a printing liquid is coated on a blanket on the printing roller, a printing pattern is formed on the printing roller by using a cliché, and the printing pattern is transcribed to a substrate, thereby forming a desired thin film.
An extent of dry of the printing liquid coated on the printing roller has time dependence such that a shape of the printing liquid formed on the cliché varies with the extent of dry. That is, the extent of dry of the printing liquid formed on the printing roller varies with positions on the cliché. Since one side of the cliché 30 is brought into contact with the printing roller 10 at an initial stage as shown in FIG. 1A, though the printing liquid 20 on the printing roller 10 is transcribed to the cliché 10 properly, since the other side of the cliché 30 is brought into contact with the printing roller 10 later than the one side of the cliché 30 as shown in FIG. 1B, dropping viscosity of the printing liquid formed on the printing roller 10, the printing liquid 20 can not be transcribed from the printing roller 10 to the cliché 10, properly. The failure of proper transcription of the printing liquid 20 from the printing roller 10 to the cliché 30 causes defective thin film formed on the substrate when the substrate is brought into contact with the printing roller 10. According to this, as shown in FIG. 2, since the thin film pattern varies with positions on the substrate 1, uniformity of the thin film pattern becomes poor.